This invention relates to printing presses, to web-fed rotary presses, and to a web supply mechanism for such presses. More specifically, the invention deals with improved means in a web supply mechanism for rotatably holding two or more webs of paper or like printable material in roll form, featuring provisions for axially shifting web rolls of different widths or axial dimensions to, and rotatably holding them in, different preassigned working positions from which the webs are to be delivered to a printing section by being conventionally spliced one to the next.
Web supply mechanisms accommodating web rolls of different widths have been known and used extensively in conjunction with web-fed rotary printing presses. Among such known mechanisms are the one taught by U.S. Pat. No. 1,980,879. It suggests pairs of web roll carrier arms mounted to a rotary shaft in circumferentially spaced positions thereon, with each pair of carrier arms disposed opposite each other axially of the shaft for movement toward and away from each other. Each carrier arm has mounted thereto an internally screw-threaded sleeve for engagement with an externally threaded rod which is rotatably mounted to the shaft and which extends parallel to its axis. The two threaded rods, associated with each pair of carrier arms, are independently driven bidirectionally in order to adjust the spacing between the carrier arms to the width of the web roll to be mounted therebetween.
An objection to this prior art device is the absence of means for jointly moving each pair of carrier arms together with the web roll supported therebetween, in order to bring the web roll to the exact working position axially of the rotary shaft. Even though each carrier arm pair are simultaneously movable in the same direction by synchronous rotation of the threaded rods, they are not mechanically coupled together. Moving two mechanically unconnected parts by two separate drive means in exact synchronism may be possible but certainly is not practical.
U.S. Pat. No. 3,326,487 teaches another web supply mechanism comprising fixed carrier arms immovably mounted to a rotary shaft adjacent one end thereof, and movable carrier arms slidably mounted to the shaft for movement along its axis toward and away from the respective fixed carrier arm. The movable carrier arms carry pinions which are engaged with racks on the rotary shaft. The spacings between the fixed and the movable arms are therefore adjustable to the widths of the web rolls to be mounted therebetween, as bidirectional rotation is imparted to the pinions.
This second prior art device possesses the same weakness as the first described one: Each pair of movable and fixed arms are of course not jointly movable for fine repositioning of the web roll. Another disadvantage is that web rolls of different widths can be positioned only against the fixed carrier arms.
Japanese Unexamined Patent Publication No. 7-285709 proposes a more sophisticated web roll positioning system, comprising actuators for simultaneously moving each pair of web roll carrier arms toward and away from each other, synchronizer means for synchronous operation of the arm actuators, and repositioning means for moving the synchronizers axially of the rotary shaft on which the carrier arms are mounted. It also teaches use of truncated-cone-shaped bosses on the distal ends of the carrier arms. With the synchronous travel of each pair of carrier arms toward each other, the bosses are to be inserted in, and frictionally caught by, the opposite ends of the tubular core of the web roll. Thus is the web roll rotatably supported between the carrier arms and, whatever its width may be, positioned centered between the opposite ends of the rotary shaft. Further, by the repositioning means, each pair of carrier arms together with the web roll mounted therebetween are jointly movable in either of the opposite axial directions of the shaft for fine readjustment of the roll position.
This third conventional positioning system is explicitly designed to position web rolls of different widths centrally of the rotary shaft. The repositioning means permit readjustment of the roll position only in the neighborhood of the central position on the shaft. It has therefore been impossible to place a web roll in offset positions on the shaft, that is, against either of the opposite extremities of the shaft.
An additional objection to this known system concerns the conical bosses on each pair of carrier arms which are forced into the opposite ends of the tubular core of the web roll for rotatably supporting the same between the carrier arms. By reaction, then, the bosses exert torsional stresses on the carrier arms, particularly at the proximal ends of the carrier arms where they are slidably mounted on the rotary shaft. The carrier arms so stressed demand inordinately large amounts of torque from the repositioning means for traveling axially of the shaft together with the web roll. Worse yet, the apparatus has suffered immensely in durability.